Modern C++ Design. Generic Programming and Design Patterns Applied. Andrei Alexandrescu. .~Addison-Wesley

Transcription

1 Modern C++ Design Generic Programming and Design Patterns Applied Andrei Alexandrescu.~Addison-Wesley Boston " San Francisco " New York " Toronto " Montreal London " Munich " Paris " Madrid Capetown " Sydney + Tokyo " Singapore " Mexico City

2 Contents Foreword by Scott Meyers Foreword by John Vlissides Preface Acknowledgments xi xv xvii xxi Part I Techniques Chapter 1 Policy-Based Class Design 1.1 The Multiplicity of Software Design The Failure of the Do-It-All Interface 1.3 Multiple Inheritance to the Rescue? The Benefit of Templates 1.5 Policies and Policy Classes Enriched Policies Destructors of Policy Classes Optional Functionality Through Incomplete Instantiation Combining Policy Classes Customizing Structure with Policy Classes Compatible and Incompatible Policies Decomposing a Class into Policies Summary 20

3 Vi Contents Chapter 2 Techniques 2.1 Compile-Time Assertions 2,2 Partial Template Specialization 2.3 Local Classes 2.4 Mapping Integral Constants to Types 2.5 Type-to-Type Mapping 2.6 Type Selection 2.7 Detecting Convertibility and Inheritance at Compile Time 2.8 A Wrapper Around type-i nfo 2.9 NuI ltype and EmptyType 2.10 Type Traits 2.11 Summary Chapter 3 Typelists The Need for Typelists Defining Typelists Linearizing Typelist Creation Calculating Length Intermezzo Indexed Access Searching Typelists Appending to Typelists Erasing a Type from a Typelist Erasing Duplicates Replacing an Element in a Typelist Partially Ordering Typelists 61 3,13 Class Generation with Typelists Summary Typel i st Quick Facts 75 Chapter 4 Small-Obj ect Allocation 4.1 The Default Free Store Allocator 4.2 The Workings of a Memory Allocator 4.3 A Small-Object Allocator 4.4 Chunks 4.5 The Fixed-Size Allocator 4.6 The Smal 1 objal 1 ocato r Class 4.7 A Hat Trick 4.8 Simple, Complicated, Yet Simple in the End 4.9 Admirtistrivia 4.10 Summary 4.11 Small-Object Allocator Quick Facts

4 Contents Vii Part 11 Components 97 Chapter 5 Generalized Functors The Command Design Pattern Command in the Real World C++ Callable Entities The Fun ctor Class Template Skeleton Implementing the Forwarding Functor : :operator() Handling Functors Build One, Get One Free Argument and Return Type Conversions Handling Pointers to Member Functions Binding Chaining Requests Real-World Issues 1. The Cost of Forwarding Functions Real-World Issues u: Heap Allocation Implementing Undo and Redo with Functor Summary Functor Quick Facts 126 Chapter 6 Implementing Singletons 129 6,1 Static Data + Static Functions!= Singleton The Basic C++ Idioms Supporting Singleton Enforcing the Singleton's Uniqueness Destroying the Singleton The Dead Reference Problem Addressing the Dead Reference Problem (I): The Phoenix Singleton Addressing the Dead Reference Problem (1:C) : Singletons with Longevity Implementing Singletons with Longevity Living in a Multithreaded World Putting It All Together Working with Si ngl etonhoi der Summary ngl etonhoi der Class Template Quick Facts 155 Chapter 7 Smart Pointers Smart Pointers The Deal Storage of Smart Pointers Smart Pointer Member Functions 161

5 viii Contents 7.5 Ownership-Handling Strategies 7.6 The Address-of Operator 7.7 Implicit Conversion to Raw Pointer Types 7.8 Equality and Inequality 7.9 Ordering Comparisons 7.10 Checking and Error Reporting 7.11 Smart Pointers to const and const Smart Pointers 7.12 Arrays 7.13 Smart Pointers and Multithreading 7.14 Putting It All Together 7.15 Summary 7.16 SmartPtr Quick Facts Chapter 8 Object Factories The Need for Object Factories Object Factories in C++ : Classes and Objects Implementing an Object Factory Type Identifiers Generalization Minutiae Clone Factories Using Object Factories with Other Generic Components Summary Facto ry Class Template Quick Facts C1 onefactory Class Template Quick Facts 217 Chapter 9 Abstract Factory The Architectural Role of Abstract Factory A Generic Abstract Factory Interface 9.3 Implementing 223 AbstractFactory 9.4 A Prototype-Based 226 Abstract Factory Implementation 9.5 Summary AbstractFacto 233 ry and ConcreteFacto ry Quick Facts 233 Chapter 10 Visitor 10.1 Visitor Basics Overloading 235 and the Catch-All Function 10.3 An 242 Implementation Refinement : The Acyclic Visitor 10.4 A Generic Implementation 243 of Visitor 10.5 Back to the "Cyclic" 248 Visitor 10.6 Hooking Variations Summary Vi sitor Generic Component Quick Facts 261

6 Contents ix Chapter 11 Multimethods What Are Multimethods? When Are Multimethods Needed? Double Switch-on-Type : Brute Force The Brute-Force Approach Automated Symmetry with the Brute-Force Dispatcher The Logarithmic Double Dispatcher FnDi spatch er and Symmetry Double Dispatch to Functors Converting Arguments: stati c_cast or dynami c_cast? Constant-Time Multimethods : Raw Speed Bas-icDispatcherandBasicFastDispatcherasPolicies Looking Forward Summary Double Dispatcher Quick Facts 297 Appendix A Minimalist Multithreading Library 307. A.1 A Critique o Multithreading 302 A.2 Loki's Approach 303 A.3 Atomic Operations on Integral Types 303 A.4 Mutexes 305 A.5 Locking Semantics in Object-Oriented Programming 306 A.6 Optional volatile Modifier 308 A.7 Semaphores, Events, and Other Good Things 309 A.8 Summary 309 Bibliography 317.